Hypertext Help with LaTeX

Declarations

A declaration is a LaTeX command that does not act on an argument,
but which changes the way LaTeX prints the following text or which changes
the value or meaning of some command or
counter.

Scope

The scope of a declaration begins with the declaration
command itself and is ended by the first right
brace (}) or \end{} command whose matching
left brace ({) or \begin{} precedes the declaration.
However, the \begin{} and \end{} of environments
you create yourself, for example, with the
\newenvironment command, do not
count for calculating the scope of declarations.

The declaration is in effect within its scope, exept that it may be
countermanded by another declaration whose scope is a subset.

However, some declarations are global; they are in effect until
countermanded by another declaration. They include